Influences of composition and temperature on the behaviors of a binary mixture containing methanol and 1-ethylimidazole

As a further investigation on the binary mixtures containing 1-alkylimidazole, over the whole composition range and at atmospheric pressure, density, ρ, sound velocity, u, of binary system of x 1-ethylimidazole (abbreviated as 1-Eim) + (1-x) methanol, were measured at temperatures (293.15–328.15) K; refractive index, n_D, and viscosity, η, of them were determined at temperatures (293.15–318.15) K; ¹H NMR, δ_H, is measured at 288.15 K; isobaric thermal expansivity, α_p, isentropic compressibility, κ_S, excess and deviation properties were calculated. The excess enthalpy and Gibbs free energy were predicted by COSMO-RS model. All the properties indicate that the real mixing process is a spontaneous enthalpy-driving process with liquid structure more ordered, and a lower temperature more benefits the process. There are stronger attractive interactions in the mixture than in pure liquids. The H-bonded interactions are the main attractive interactions in the mixture, followed by the electrostatic/misfit interaction and the Van der Waals force. A H-bonded network with a ration of methanol:1-Eim = 1:1 appears in the mixture, and reaches its maximum amount at x about 0.4; via the N···HO, the rearrangement of electron densities occurs where protons of 1-Eim and hydroxyl all show electron-donating abilities while methyl protons of methanol show electron-withdrawing ability.